Distal Valve for a Catheter

ABSTRACT

A bi-directional valve assembly, including valves for use in closed-ended catheters or other elongate tubular devices, is disclosed. In one embodiment, a catheter assembly for insertion into a body of a patient is disclosed and comprises an elongate catheter tube including an outer wall that at least partially defines at least one lumen that extends between a proximal end and a closed distal end thereof. The catheter tube includes a valve assembly that in turn includes a linear slit valve defined through the outer wall of a distal segment of the catheter tube, and a deformation region. The deformation region includes a compliant segment disposed in the outer wall of the catheter tube and a thinned portion of the outer wall. The compliant segment and thinned portion of the deformation region cooperate to preferentially deform the outer wall and open the slit valve during aspiration through the catheter tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/621,276, filed Apr. 6, 2012, and titled “Distal Valvefor a Catheter,” which is incorporated herein by reference in itsentirety.

BRIEF SUMMARY

Briefly summarized, embodiments of the present invention are directed toa valve assembly, including valves for use in closed-ended catheters orother elongate tubular devices. The valve is employed to provide aselectively openable, bi-directional barrier between the interior andthe exterior of the catheter. When the valve is at rest, the valve isclosed so as to prevent the passage of air or fluids. When a sufficientaspiration or infusion force is applied, the valve opens either inwardlyor outwardly to permit the passage of fluids therethrough. Once theforce is removed, the valve returns to its closed position. As will beseen, the valve assembly is configured so as to provide reliable, lowfriction opening of the valve while also preventing the unintendedcatching of valve surfaces during operation.

In one embodiment, a catheter assembly for insertion into a body of apatient is disclosed and comprises an elongate catheter tube includingan outer wall that at least partially defines at least one lumen thatextends between a proximal end and a closed distal end thereof. Thecatheter tube includes a valve assembly that in turn includes a linearslit valve defined through the outer wall of a distal segment of thecatheter tube, and a deformation region disposed on the distal segment.The deformation region includes a compliant segment disposed in theouter wall of the catheter tube and a thinned portion of the outer wall.The compliant segment and thinned portion of the deformation regioncooperate to preferentially deform the outer wall of the catheter tubewhen an aspiration force is present in the at least one lumen so as toassist in opening the slit valve.

These and other features of embodiments of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of embodiments of theinvention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the present disclosure will be renderedby reference to specific embodiments thereof that are illustrated in theappended drawings. It is appreciated that these drawings depict onlytypical embodiments of the invention and are therefore not to beconsidered limiting of its scope. Example embodiments of the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 is a perspective view of an implantable access port and attachedcatheter assembly, which serve as one example environment whereembodiments of the present disclosure can be practiced;

FIGS. 2A-2C are various views of a distal segment of a catheter tube inaccordance with one embodiment;

FIGS. 3A-3D show various cross sectional views of the catheter tubedistal segment of FIGS. 2A-2C showing operation of a distal valve inaccordance with one embodiment;

FIG. 4 is a graph showing aspects of operation of the distal valve ofFIGS. 3A-3D according to one embodiment;

FIGS. 5A-5C show various views of a catheter tube distal segmentaccording to one embodiment; and

FIGS. 6A-6B show various cross sectional views showing operation of adistal valve of a catheter tube according to one embodiment.

DETAILED DESCRIPTION OF SELECTED EMBODIMENTS

Reference will now be made to figures wherein like structures will beprovided with like reference designations. It is understood that thedrawings are diagrammatic and schematic representations of exemplaryembodiments of the present invention, and are neither limiting nornecessarily drawn to scale.

For clarity it is to be understood that the word “proximal” refers to adirection relatively closer to a clinician using the device to bedescribed herein, while the word “distal” refers to a directionrelatively further from the clinician. For example, the end of acatheter placed within the body of a patient is considered a distal endof the catheter, while the catheter end remaining outside the body is aproximal end of the catheter. Also, the words “including,” “has,” and“having,” as used herein, including the claims, shall have the samemeaning as the word “comprising.”

Embodiments of the present invention are generally directed to valveassemblies, including valves for use in closed-ended catheters or otherelongate tubular devices. The valve is employed to provide a selectivelyopenable, bi-directional barrier between the interior and the exteriorof the catheter. When the valve is at rest, the valve is closed so as toprevent the passage of air or fluids. When a sufficient aspiration orinfusion force is applied, the valve opens either inwardly or outwardlyto permit the passage of fluids therethrough. Once the force is removed,the valve returns to its closed position. As will be seen, the valveassembly is configured so as to provide reliable, low friction openingof the valve while also preventing the unintended catching of valvesurfaces during operation.

FIG. 1 shows a port/catheter assembly (“assembly”), generally designatedat 10, as an example of an environment where the valve assembly can beemployed, according to one embodiment. As shown, the assembly 10includes an implantable access port 12 and attached catheter 20configured for implantation into a body of a patient so as to providefluid access to the vasculature of the patient. The port 12 includes abody 14 and a needle-penetrable septum 16 that covers a fluid reservoirdefined by the body. The catheter 20 includes an elongate and flexible,or compliant, catheter tube 22 that defines one or more lumens 43 (FIG.2C) extending from a proximal end 22A to a distal end 22B of the tube.The proximal end 22A of the catheter tube 22 fits over a stem extendingfrom the port body 14 and is secured thereto via a connector 24.

A valve assembly 30 according to one embodiment is included at a distalsegment 34 of the catheter tube 22. The distal segment 34 is shown as adiscrete piece attached via adhesive, overmolding, or other suitablebonding to a proximal portion 32 of the catheter tube via a skivedinterface 33, though in other embodiments the distal segment can beintegrally formed with the proximal tube portion. The distal end 22B ofthe catheter tube 20 is closed, such as via a plug 35 or other suitableclosure scheme.

FIGS. 2A-2C show further details of the valve assembly 30 according toone embodiment. A slit valve 36 is shown, including a longitudinallydefined slit 38 that extends through an outer wall 42 defining thecatheter tube 20 to provide valved access to the lumen 43. The slitvalve 36 is configured so as to deflect outwardly when a sufficientpositive pressure is present in the lumen 43 such that fluids can passfrom the lumen into the vessel or other location of the patient body inwhich the catheter is disposed. Passage of fluids from the catheter tubelumen is also referred to herein as “infusion.” The slit valve 36 isfurther configured to deflect inwardly when a sufficient negativepressure is present in the lumen 43 such that fluids can be drawn intothe lumen, also referred to herein as “aspiration.”

As best seen in FIG. 2C, the slit valve 36 includes a longitudinallength L and a width W. In one embodiment, a ratio of length L to widthW of the slit valve 36 has a value of about 10:1 so as to providesufficient restorative force to return to its undeflected, or at-rest,position shown in FIG. 2B. Of course, other slit length-to-width ratioscan be employed, including within the range of from about 8:1 to about15:1, in one embodiment.

It is noted here that a slit valve is readily deflectable to providefluid infusion into the vessel as sufficient positive pressure isreadily producible within the catheter tube lumen 43 via connection ofthe catheter with pressure-producing external apparatus. Deflection ofthe slit valve 36 to produce aspiration into the catheter tube lumen 43under an infusion force, however, is relatively more difficult asnegative pressures only up to −1 atmosphere (“atm”) are possible. Assuch, any slit valve solution should ensure adequate and reliable valveopening under negative pressure, i.e., under aspiration force, withinthe catheter tube lumen. Correspondingly, the slit valve should also beconfigured to close adequately and securely when no slit opening force,i.e., aspiration force or infusion force, is present.

In accordance with one embodiment, a deformation region is included inthe valve assembly 30 so as to assist in deflection of the slit valve 36during aspiration. The deformation region preferentially deforms when asufficient negative pressure is present in the lumen 43 of the cathetertube 22, such as an aspiration force that is present when the catheter20 is being employed for aspiration of fluids therethrough. As seen inFIGS. 2A-2C, the deformation region in the present embodiment isimplemented as a compliant segment 40 that includes a segment ofmaterial forming the outer wall 42 that is softer in durometer, orhardness, relative to the surrounding material of which the remainder ofthe distal segment outer wall is composed. Generally, a durometer ratingfor the compliant segment material at about 10 to about 20 less thanthat of the surrounding outer wall material is sufficient to provide thedesired preferential deformation of the compliant segment to open theslit valve, as described further below.

In light of the above, in the present embodiment the compliant segmentmaterial includes silicone of durometer rating about 50 while thesurrounding distal segment outer wall includes silicone of about 70. Theproximal tube portion 32 also includes silicone and possesses adurometer of about 50, though this may vary. It is appreciated that thespecific durometer ratings of the aforementioned components can varyaccording to application, material used, amount of desireddeformation/valve opening, etc. Further, materials other than siliconecan be used in the outer wall of the valve assemblies/distal segmentsdescribed herein. Generally, the material used for catheter assembliesfor patient insertion should be biocompatible, possess an acceptabledurometer range, low tendency for creep, be able to bond with othercatheter tube portions if necessary, and be able to retain the desiredphysical form of the catheter tube such that the catheter can operate asintended. Examples of suitable materials that can be employed includesilicone, polyurethane, polyurethane/silicone mixtures,polycarbonate/polyurethane copolymers, etc. In the case of polyurethane,a coating may be applied to the faces of the slit valve to preventknitting together of the slit faces. Such a coating can includeparylene, for instance.

The length of the compliant segment 40 is slightly larger than that ofthe slit 38 of the slit valve 36, though this and the other dimensionsof the compliant segment can be varied from what is shown and describedherein. The circumferential breadth of the compliant segment 40 is shownin FIGS. 2C and 3A to extend in the present embodiment about a quarterof the circumference of the catheter tube when viewed cross-sectionally(FIG. 3A).

The compliant segment 40 is positioned in a spaced-apart relationshipwith respect to the slit valve 36 so as to assist in opening of the slitvalve when the compliant segment preferentially deforms under anaspiration force as explained further below. As seen in FIGS. 2C and 3A,the position of the compliant segment 40 extends from about 90 degreesto about 180 degrees circumferentially away from the slit valve 36,assuming the slit valve is positioned a circumferential position of 0degrees. Again, the particular position of the compliant segment canvary.

As best illustrated in FIGS. 2C and 3A, the deformation region in thepresent embodiment is further implemented as a thinned portion 44 of theouter wall 42 of the catheter tube 22. As shown, the thinned portion 44is tapered in its thickness in the present embodiment, with it beingthinnest at a position substantially opposite the slit valve 36, i.e.,about 180 degrees circumferentially away from the slit valve. From thisthinnest point, the thinned portion 44 tapers up in thickness to thefull thickness of the outer wall 42 near about 90 degreescircumferentially away from the slit valve 36. FIG. 2C shows that thelongitudinal extent of the thinned portion 44 is shorter than andapproximately centered within the length of the compliant segment 40.

Thus the deformation region, including the compliant segment 40 and thethinned portion 44, is positioned in a circumferentially offsetconfiguration with respect to the slit valve 36. This offsetconfiguration enhances the desired preferential deformation of thecatheter tube outer wall during aspiration, as will be described furtherbelow. As before, note that the length, circumferential extent,tapering, position, and other aspects of the thinned portion can varyfrom is shown and described herein. For instance, in one embodiment, thethinned portion is not tapered but is uniformly thin. In anotherembodiment, the slit valve can be disposed within the thinned portion,compliant segment, or both. These and other modifications are thereforecontemplated.

In the illustrated embodiment, the length of the slit 38 is about 0.250inch, the length of the compliant segment 40 is about 0.5620 inch, thelength of the thinned portion 44 is about 0.290 inch, the minimumthickness of the thinned portion is about 0.009 inch, and the thicknessof the un-thinned outer wall 42 is about 0.019 inch. These dimensionscan be altered in other embodiments.

FIGS. 3A-3D depict various details regarding operation of the valveassembly 30, in particular, opening of the slit valve 36 duringaspiration of fluids from outside of the catheter tube 22 to within thelumen 43 thereof. Such aspiration is used, for example, to remove bloodor other fluids from the patient's body via the catheter 20/port 10.FIG. 3A shows that when an aspiration force—indicated by aspirationforce arrows 46—is present within the catheter tube lumen 43, aresultant force is produced in the outer wall 42 of the catheter tube22. As shown in FIG. 3A this force, indicated by force arrows 48A, worksto prevent opening of the slit 38 of the slit valve 36.

FIG. 3B shows that, because of the inclusion of the deformation regionin the catheter tube outer wall 42, including the compliant segment 40and the thinned portion 44, preferential deformation of the outer wallby the aspiration force occurs proximate the deformation region, as seenon the bottom of the catheter tube in FIG. 3.

The preferential deformation of the outer wall 42 of FIG. 3B is shown ingreater detail in FIG. 3C. In particular, the offset position of thecompliant segment 40 and thinned portion 44 of the deformation regioncauses the outer wall proximate the deformation region to preferentiallydeform, or buckle, before other wall portions, due to the relativelyweaker strength of the wall in this region as a result of its thinnessand relative softness. This buckling alters the forces present in theouter wall as shown by force arrows 48B. Specifically, the force arrows48B proximate the slit 36 show that the outer wall force at the slitfacilitate its opening.

Further buckling of the deformation region soon causes sufficientopening of the slit valve 36 that a face 50 of the slit 36 will deflect,completing opening of the slit valve and enabling fluid to enter thecatheter tube lumen 43 as part of an aspiration procedure. Force arrows48B in FIG. 3D show how the outer forces direct the slit facedeflection. Once the aspiration force is removed, the slit valveresiliently repositions itself as shown in FIG. 3A.

FIG. 4 shows a graph 60 including a curve 62 showing the negative(aspiration force) pressures at which the slit valve 36 of the valveassembly 30 of FIGS. 2A-3D opens in one embodiment. As shown, the slitvalve 36 is configured to reliably open at between about −2 and −3 psi.As already mentioned, the valve assembly and deformation region can beconfigured so as to modify the pressure(s) at which the slit valveopens, or other aspects of valve operation. For instance, the magnitudeof the thinned portion, length and position of the slit valve or thinnedportion, etc. can be modified to adjust the pressure at which the slitvalve opens.

In one embodiment, the catheter tube, valve assembly, and deformationregion described above can be formed in one embodiment by first formingthe proximal tube portion 32 (FIG. 1) of the catheter tube by any one ofsuitable processes, including extrusion, molding, etc. The distal end ofthe proximal tube portion 32 is skived to define the skived interface33, then placed in a mold, where the distal segment 34 of the cathetertube 22 is overmolded on to the proximal tube portion.

Note that a core pin is inserted into the tube lumen prior to the aboveovermolding so that the volume of the catheter tube outer wall 42 wherethe compliant segment 40 is to be disposed is occupied by a portion ofthe core pin. A subsequent overmolding with the core pin removed is thenperformed to add the relatively softer compliant segment 40 and thinnedportion 44. A temporary clocking feature extending from the distal endof the completed catheter tube 22 is also molded via this subsequentovermolding to enable the manufacturer to determine proper placement ofthe slit 38 of the slit valve 36, in one embodiment. The slit 38 is thendefined through the catheter tube outer wall 42. The clocking feature isthen removed from the distal end and the plug 35 attached to thecatheter tube distal end 22B to close the end thereof. Note that theclocking feature can take one of many forms. Note that in oneembodiment, the plug 35 can be attached prior to cutting the slit 38.Note also that other or additional steps can be added to the abovemanufacturing process; as such, the above discussion is not meant to belimiting in any way.

Notwithstanding the above discussion, note that the deformation regionin one embodiment can include only one of either the compliant segmentor the thinned region while still enabling preferential deformation ofthe catheter tube outer wall to facilitate opening of the slit valve.Also, the deformation region can include other aspects in addition toone or both of the compliant segment and the thinned portion in order tofacilitate slit valve opening.

Note also that, while it is described above in connection with medicalcatheters, the valve assemblies and deformation regions described hereincan be employed in other types of catheters and elongate tubulardevices. Also, though shown proximate the distal catheter end, the valveassembly and deformation region can be disposed at other longitudinallocations along the catheter tube.

FIGS. 5A-5C show various details of a valve assembly 130 including adeformation region according to another embodiment. As before, the valveassembly 130 is included on a distal portion of the catheter tube 22. Inthe present embodiment, the valve assembly 130 includes a distal supportsegment 134 that includes a relatively hard durometer material, such assilicone of durometer of about 70, for instance. As best seen in FIG.5B, the distal support segment 134 extends from the skived distal end ofthe proximal tube portion 32 of the catheter tube 22 to a predetermineddistance away from the distal end of the catheter tube in a steppedconfiguration. In another embodiment, the distal support segment can beintegrally formed with the proximal tube portion 32.

As shown, the deformation region in the present embodiment isimplemented as both a compliant segment 140 and a corresponding thinnedportion 144 of the catheter tube outer wall 142. The compliant segment140 includes a relatively soft durometer material with respect to thedurometer of the material of which the distal support segment 134 iscomposed. In the present embodiment, silicone of durometer of about 50is used for the compliant segment 140. The compliant segment 140 extendsdistally in a stepped configuration corresponding to the steppedconfiguration of the distal support segment 134 so as to complete theouter wall 142 and lumen of the distal portion of the catheter tube 22.As before, a plug 135 or other suitable closure is included to close thedistal end of the catheter tube 22. Note that the distal support segment134 and compliant segment 140 can be formed via successive corepin-assisted injection molding procedures as before, includingovermolding and/or rapid injection molding, or by other suitableprocesses, in one embodiment. Note also that, though in the presentembodiment the durometer ratings of the material used for the distalsupport segment 134 (durometer about 70) and the compliant segment 140(durometer about 50) differ by about 20, in other embodiments thedurometer ratings differ by more or less, such as from about 10 to about30, in one embodiment. Further note that the catheter tube 22 in thepresent embodiment includes a relatively softer durometer as compared tothe durometer of the distal support segment 134 so as to enable thecatheter tube 22 to maneuver relatively easily through the patientvasculature during insertion. It is also appreciated that, in oneembodiment, the catheter tube itself can include a durometer thatenables it to serve as the distal support segment thus negating the needfor a separate distal support segment to be attached to the cathetertube.

The distal support segment 134 defines a first face 138A of a slit 138,while the compliant segment 140 defines a second face 138B of the slitto define a slit valve 138. In one embodiment the length of the slit 138is about 0.27 inch, but the length can vary according to desire or need.

The first face 138A, second face 138B, or both faces of the slit 138 caninclude a low friction coating or other substance to prevent stickingtogether of the faces. In the present embodiment, a polymer coating,such as parylene, is included on the first face 138A of the slit 138,which is defined by the distal support segment 134. Such a coating canbe applied via vapor deposition or other suitable process. In anotherembodiment a coating including silicone with a fluorine additive can beapplied to the face(s) 138A/B. In yet another embodiment, aself-lubricating silicone can be used to form the distal support segment134, the compliant segment 140, or both components, thus providing aself-lubricating solution for the valve slit to prevent valve hang-during closing and knitting together of the slit faces. These and otherlubricious and/or low-friction solutions are contemplated. Note thatsuch coatings can be used with a variety of base materials that form thedistal support segment and/or compliant segment. For instance, in oneembodiment a parylene coating can be included on one or both the slitfaces when the distal support segment, the compliant segment, or bothcomponents include polyurethane.

In addition, in one embodiment the lubricious or low-friction coatingcan be applied to the first slit face before the compliant segment ismolded to the distal support segment. This enables the slit valve to beautomatically defined by virtue of the two faces being unable to adhereto one another. In this and other embodiments herein, note that theforce required to open the slit valve can vary according to variousfactors including friction between the slit faces, slit length,durometers of the compliant segment and distal support segment, valvewall thickness, etc.

FIGS. 5A and 5C show that the deformation region is further implementedin the present embodiment as a thinned portion 144 longitudinallycentered on the slit valve 136 and disposed such that the thinnestportion thereof is adjacent to the second slit face 138B. Note that thelongitudinal length of the thinned portion 144 is less than that of theslit 138, though the dimensions shown and described herein can vary.Indeed, the length, width, tapering, position, etc. of the thinnedportion 144 can be modified as appreciated by one skilled in the art.

In the present embodiment, the deformation region including thecompliant segment 140 and thinned portion 144 is configured topreferentially and bi-directionally deform near the slit valve 136 underpressure to open the slit 138, while the distal support segment 134 isless apt to deform. Indeed, during infusion of fluids through thecatheter 22, the compliant segment 140 proximate the slit valve 136deforms radially outward so as to enable fluids to pass out the lumen143 of the catheter tube 22 through the slit 138. Correspondingly,during fluid aspiration, the compliant segment 140 proximate the slitvalve 136 deforms radially inward so as to enable fluids to enter thelumen 143 of the catheter tube 22. Once infusion or aspiration forcesare removed, the slit valve 136 resiliently returns to its rest state tore-seal the catheter tube lumen 143. Note that the deformation regionjust described above assists in preventing “hang up” of the first face138A of the slit 138 against the second face 138B when the slit valve136 returns to a closed position.

In another embodiment, it is appreciated that the thinned portion of thedeformation region can thin from the outside of the catheter tube outerwall such that the inner diameter of the catheter tube lumen isuniformly smooth. Note that while the present discussion describes thevalve assembly 130 as including a single lumen catheter, in otherembodiments one or more lumens of a multi-lumen catheter tube mayinclude valve assemblies as described herein. Note also that all or someof the deformation region, compliant segment, and/or distal supportsegment can be color-coded to indicate a certain aspect of the catheter,such as its ability to withstand pressures associated with powerinjection, for instance.

FIGS. 6A and 6B show the catheter tube 22 including a deformation regionaccording to another embodiment, wherein a thinned portion 244 of anouter wall 242 of the catheter tube is disposed at a spaced apartlocation with respect to a slit valve 236. As shown, in FIG. 6B, thethinned portion 244 of the deformation region in the illustratedposition assists in readily opening the slit valve 236 under anaspiration force. Thus, it is seen that the position of the thinnedportion of the deformation region can be varied while still fallingwithin the principles of the present embodiments.

Embodiments of the invention may be embodied in other specific formswithout departing from the spirit of the present disclosure. Thedescribed embodiments are to be considered in all respects only asillustrative, not restrictive. The scope of the embodiments is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. An elongate tubular device, comprising: aflexible, elongate tube including an outer wall defining at least onelumen that extends between a proximal end and a closed distal endthereof; and a valve assembly included in the tube and including: a slitvalve defined through the outer wall; and a deformation region includinga compliant segment disposed in the outer wall in relation to the slitvalve, the compliant segment preferentially deforming under aspirationforces in the at least one lumen so as to assist in opening the slitvalve.
 2. The device as defined in claim 1, wherein deformation of thecompliant segment alters forces in the outer wall of the tube so that atleast one face of the slit valve can deflect to open the slit valve. 3.The device as defined in claim 1, wherein the deformation regionincludes a lower material strength relative to surrounding portions ofthe outer wall of the tube.
 4. The device as defined in claim 1, whereinthe compliant segment is more compliant relative to surrounding portionsof the outer wall of the tube.
 5. The device as defined in claim 1,wherein the compliant segment includes a material possessing a seconddurometer less than a first durometer possessed by a material of thesurrounding portions of the outer wall of the tube.
 6. The device asdefined in claim 5, wherein a durometer difference of about 20 existsbetween the first and second durometers.
 7. The device as defined inclaim 1, wherein both the slit valve and the compliant segment extendlongitudinally along the outer wall of the tube.
 8. The device asdefined in claim 7, wherein the compliant segment is positioned in acircumferentially spaced apart position relative to the slit valve. 9.The device as defined in claim 7, wherein the compliant segment ispositioned adjacent the slit valve.
 10. The device as defined in claim9, wherein the compliant segment of the outer wall defines at least oneface of the slit valve.
 11. The device as defined in claim 1, whereinthe valve assembly further includes a support segment including amaterial of first durometer that defines a first face of the slit valve,the compliant segment including a material of second durometer thatdefines a second face of the slit valve, the second durometer less thanthe first durometer.
 12. The device as defined in claim 1, wherein theelongate tubular device includes a catheter for insertion into a body ofa patient, and wherein the valve assembly is disposed proximate thedistal end of the catheter.
 13. The device as defined in claim 1,wherein the slit valve includes a length-to-width ratio of about 10 to1, the width of the slit valve measured as the thickness of the outerwall.
 14. The device as defined in claim 1, wherein the deformationregion further includes a thinned portion of the outer wall of the tubethat is thinner relative to surrounding portions of the outer wall. 15.The device as defined in claim 14, wherein the thinned portion issubstantially aligned with the compliant segment, the thinned portiontapered in a circumferential direction between a minimum and a maximumthickness.
 16. A method for forming a closed-ended catheter, the methodcomprising: forming an elongate catheter tube including an outer wallthat defines at least one lumen, the catheter tube including a distalsegment; defining a slit valve through the outer wall of the distalsegment; and including a compliant segment in the outer wall of thedistal segment, the compliant segment including a durometer below thatof surrounding portions of the outer wall, the compliant segmentpositioned relative to the slit valve such that the compliant segmentpreferentially deforms when an aspiration force is present in the atleast one lumen to assist in opening the slit valve.
 17. The method forforming as defined in claim 16, wherein forming the catheter tubefurther comprises: defining a proximal tube portion; skiving a distalend of the proximal tube portion; and molding a distal tube portion onto the proximal tube portion to define the distal segment of thecatheter tube.
 18. The method for forming as defined in claim 17,wherein forming the catheter tube and including the compliant segmentfurther comprise: placing a core pin in the at least one lumen of theproximal tube portion, the core pin blocking a volume where thecompliant portion will be disposed; molding the distal tube portion onto the proximal tube portion to define the distal segment of thecatheter tube; removing the core pin; and overmolding the compliantsegment on to the distal segment of the catheter tube.
 19. The methodfor forming as defined in claim 18, wherein the slit valve is definedafter the compliant segment is overmolded on to the distal segment ofthe catheter tube.
 20. The method for forming as defined in claim 19,further comprising attaching a plug to the distal end of the cathetertube.
 21. An elongate tubular device, comprising: an elongate tubeincluding an outer wall defining at least one lumen that extends betweena proximal end and a closed distal end thereof; and a valve assemblyincluded in the tube and including: a slit valve defined through theouter wall; and a deformation region including a thinned portion of theouter wall that is thinner relative to surrounding portions of the outerwall, the thinned portion disposed in relation to the slit valve andpreferentially deforming under an aspiration force in the at least onelumen so as to assist in the opening the slit valve.
 22. The device asdefined in claim 21, wherein the thinned portion longitudinally extendsa predetermined distance along the length of the tube.
 23. The device asdefined in claim 22, wherein the thinned portion is disposed in acircumferentially spaced-apart position between about 90 and about 180degrees from the slit valve.
 24. The device as defined in claim 21,wherein the thinned portion is positioned substantially adjacent theslit valve.
 25. The device as defined in claim 21, wherein deformationof the thinned portion alters forces in the outer wall of the tube sothat at least one face of the slit valve can deflect to open the slitvalve.
 26. The device as defined in claim 21, wherein the deformationregion further includes a compliant segment disposed in the outer wallin relation to the slit valve, the compliant segment contributing topreferential deformation under aspiration forces in the at least onelumen so as to assist in opening the slit valve.
 27. The device asdefined in claim 26, wherein the thinned region and the compliantsegment are defined in a common location of the outer wall of the tube,and wherein the thinned portion is tapered in a circumferentialdirection between a minimum and a maximum thickness.
 28. The device asdefined in claim 21, wherein the elongate tubular device includes acatheter for insertion into a body of a patient and wherein the cathetertube includes self-lubricating silicone.
 29. A catheter assembly forinsertion into a body of a patient, comprising: an elongate cathetertube including an outer wall that at least partially defines at leastone lumen that extends between a proximal end and a closed distal endthereof; and a valve assembly included in the catheter tube andincluding: a linear slit valve defined through the outer wall of adistal segment of the catheter tube; and a deformation region disposedon the distal segment and including: a compliant segment disposed in theouter wall of the catheter tube; and a thinned portion of the outerwall, wherein the compliant segment and thinned portion cooperate topreferentially deform the outer wall of the catheter tube when anaspiration force is present in the at least one lumen so as to assist inopening the slit valve.
 30. The catheter assembly as defined in claim29, wherein the compliant segment includes a durometer that is lessrelative to surrounding portions of the outer wall, wherein the thinnedportion is thinner relative to surrounding portions of the outer wall,and wherein the compliant segment and the thinned portion are disposedin a substantially common location of the outer wall.
 31. The catheterassembly as defined in claim 30, wherein the compliant segment and thethinned portion longitudinally extend a predetermined distance along thelength of the catheter and are disposed between about 180 degrees andabout 90 degrees circumferentially around the catheter tube from theslit valve so as to be offset from the slit valve.
 32. The catheterassembly as defined in claim 31, wherein the compliant segment includessilicone of a durometer rating of about 50, and wherein at least aportion of the outer wall surrounding the compliant segment includessilicone of a durometer rating of about 70.